[flashcache-dev] Why do invalidating after the completion of an uncacheable IO ?

[m***@gmail.com]

Hi,everyone!
I'm interested in the flashcache source code.But when I read this
function:flashcache_uncached_io_complete(struct kcached_job *job),and the
comments " We do invalidations before launching uncacheable IOs to disk.
But in case
of out of ordering the invalidations before launching the IOs does not
help. We need to invalidate after the IO completes."So what the meaning of
out of ordering? Why do invalidating after the completion of an
uncacheable IO ? Can
anyone help me ? thanks!